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1994 Polaris 250 Trail Boss Not Running

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Turbolag

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Discussion starter · #1 ·
Hey everyone, been a while since I posted. Wow, didn't realize how long.

So I have a project that has begun. I have a 94 Polaris 250 Trail Boss and here is the story on it.

about two years ago I was riding it in the neighborhood and all of a sudden the motor stopped running. I pulled on the hand start a couple times and the motor seized up. I couldn't pull the hand starter at all, wouldn't budge.

So I left the 4 wheeler sitting for about two years.

This past week I started removing parts to pull the motor out for a rebuild.

I thought while I was trying to decide what part to remove next I would pull the hand starter to make sure it was still seized. Nope, it moves freely now.

It doesn't start up or anything, the gas in the tank is old.

So here is my question. Should I still pull the motor and do a rebuild ? Or should I just pull the carburetor off and clean it ?

I'm guessing the carb has a lot of bad gas and gunk in it, preventing start up.

Any thoughts ?

Thanks.
 
Discussion starter · #3 ·
austinado16 said:
Step 1: Compression test
Click to expand...
This is something interesting I can add.

Two years ago when it seized up, it wasn't running correctly about a week before.

So I put a compression tester on it and it was fine.

Turns out the issues were bad fuel line and it needed a new spark plug.

About a week or two later it seized up.

With that in mind, is there anyway it could have lost compression since then ? Since it hasn't been running ?
 
#4 ·
yes it will likely be worse now! if stored without fogging the cylinders, the cylinders, start to rust. it will be fine if you test it now,but when those pieces of rust break off and leave the cylinder it won't be so good! you can run it and maybe get lucky [it is what it is type performance] ,but that is the usual scenario!
 
#5 ·
2 Stroke right? So you are saying you tested the compression before it seized? That doesn't really tell us anything now, since it's impossible to do a compression test on a seized engine and it's probably substantially lower now that something failed.

The fact that is seized up entails that there was a failure of something. Even if it comes unstuck, it won't run for long, or very well.

A 2 stroke will typically seize from a lean mixture, lack of lubrication, or somewhat rarely a mechanical failure.

Lean mixtures can stem from air leaks in the crankcase or other gaskets, or a dirty carburetor. It's usual symptoms are a spark plug with a white/silver color.

Lack of lubrication is fairly obvious. Fuel was mixed too lean, or the oil injection system failed. I've also heard of fuel separating after sitting and causing issues.

Since there aren't many moving parts in a 2 stroke, there are only a couple of mechanical failures that can happen. The most common is a tossed piston pin clip. They will usually lodge between the piston and cylinder wall and put a groove in the cylinder and trash the piston. The other is a failed piston pin bearing, but that is usually from lack of lubrication. A lower end (crankshaft or connecting rod) is possible but not as common as a top end failure.

I would pull the top end and look. Pull the engine so it's easy to reach and inspect.
 
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Discussion starter · #9 ·
Dayton_King said:
Older polaris's are known for the oil injection pump to go out often, which leads the motor to sieze. On my old I polaris I pulled the injection, and pre mix

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Click to expand...
That's what we were thinking. I want to remove the oil injector setup and just add oil to the gas in the tank.

Do you know what the oil/ gas ratio is? I was thinking 32-1 maybe?

I compression tested it about 2 months before it seized because it was not running properly. I found out the fuel line was rotted and it needed a new spark plug.

Then about 2 months later I was riding it down the road at it quit running. Th tried to pull start it and it seized up.
 
Discussion starter · #10 ·
Update: Brought the 4 wheeler to the shop and the piston is gone. It needs a rebuild

So here is my question. What should I do ?

Is it possible for me to change that motor out for a larger motor ? Like a 400 cc ?

Or can I find a rebuild kit for it anywhere? I think I saw one on ebay a while back.

Not sure what to do.
 
Discussion starter · #12 ·
CADplans said:
My daughter blew the piston out of her 1996 250 Trail Blazer doing donuts in some snow (engine over revved)

I got a piston at the dealer, it was cheap, and back together in a couple hours.
Click to expand...
The shop we brought it to is also a dealer. They used to have a Polaris dealer but not its a used bike shop. They said it would be hard to find parts for and it would cost upwards of $1500.
 
Discussion starter · #15 ·
CADplans said:
Time to talk to somebody else, I spent less than a "C" note on the entire repair.

Substituting an engine would cost more than a piston.
Click to expand...
Yea looks like I'll be doing the work myself. Haha.

I think I'll go talk to a local machine shop and get a plan together.

I'm not sure if I can order a stock piston, or if the cylinder was scarred and needs to be bored out. So I might have to order a larger than stock piston.

Maybe I can bring them the motor dissasembled and they can give me some advice.

But for $150 the Ebay rebuild kit looks nice. It has a Wiseco Piston.

I was thinking I would just bring them the kit and the motor.

Is it possible to change to a different motor ? Like if I wanted to replace the 250cc motor with a 400cc engine is that possible ?
 
#18 · (Edited)
Turbolag said:
I'm sorry for asking but what is the jug and where is it located? I've tried searching for more info on the bike but I haven't been able to find much info.
Click to expand...
It’s the top end of the engine. I rebuilt my 250 about 3 years ago. The reason I say not to buy anything is because if the cylinder wall is damaged you may need to get it machined and you may need oversized piston. If this is the case it wont be cheep.
I think it was around $90. To $100 for the machining plus all the other parts.
I did all the work myself but bought the parts at a dealer so I didn’t buy the wrong
Parts. I think I had around $400. To $500. Before I was done. Take pictures of every step for your records so you know were to put the parts back.
Start off with a manual.
Good Luck
 

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Discussion starter · #19 ·
turkey2731 said:
It’s the top end of the engine. I rebuilt my 250 about 3 years ago. The reason I say not to buy anything is because if the cylinder wall is damaged you may need to get it machined and you may need oversized piston. If this is the case it wont be cheep.
I think it was around $90. To $100 for the machining plus all the other parts.
I did all the work myself but bought the parts at a dealer so I didn’t buy the wrong
Parts. I think I had around $400. To $500. Before I was done. Take pictures of every step for your records so you know were to put the parts back.
Start off with a manual.
Good Luck
Click to expand...
Thanks man!

So you can remove the top end without it coming out ?

Did you jack it up in the air or just leave it on the tires?

I guess it will just take some trial and error.

Thanks for sharing the photo!
 
#20 ·
Turbolag said:
Thanks man!

So you can remove the top end without it coming out ?

Did you jack it up in the air or just leave it on the tires?

I guess it will just take some trial and error.

Thanks for sharing the photo!
Click to expand...
I did jack it up about a foot to save my back.:dunno:
 
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